Lithium iron phosphate (LFP) batteries are environment-friendly batteries. Compared to common lithium batteries, LFP batteries have advantages such as high safety, long cycle life, fast charge and discharge, lower weight with the same energy density and high temperature performance, and thus have favorable application prospect. For example, LFP battery packs can be applied to Electric Vehicles (EVs), Energy Storage Systems (ESSs) and the like. Common applications include electric bicycles, electric buses and the like.
An LFP battery pack is formed of multiple individual cells connected in series. Due to restrictions from manufacturing processes, there are deviations between cells, and during their use, these cells may have different self-discharges due to an increase in the number of charge-discharge cycles and impacts from storage time, temperature and the like, therefore cells in the same battery pack have different States of Charge (SoCs), thereby resulting in unequalization of cells in the same battery pack. SoC is also referred to as remaining capacity, which indicates a ratio of a remaining capacity after a battery is used for a period of time or is put aside for a long time to a capacity when the battery is fully charged, and which is expressed in percentage. SoC has a range of 0 to 1, and when SoC=0, it represents that the battery is fully discharged, and when SoC=1, it represents that the battery is fully charged.
Such non-equalization for an LFP battery pack may reduce performance of the LFP battery pack, and the life time of the LFP battery pack will be shortened. Therefore, the LFP battery pack needs to be equalized so that differences in SoCs between respective cells in the LFP battery pack are within a certain error range.